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2.3.1 Using positional notation

Positional notation is the traditional mechanism for passing arguments to functions in PostgreSQL. An example is:

SELECT concat_lower_or_upper('Hello', 'World', true);
 concat_lower_or_upper
-----------------------
 HELLO WORLD
(1 row)

All arguments are specified in order. The result is upper case since uppercase is specified as true. Another example is:

SELECT concat_lower_or_upper('Hello', 'World');
 concat_lower_or_upper
-----------------------
 hello world
(1 row)

Here, the uppercase parameter is omitted, so it receives its default value of false, resulting in lower case output. In positional notation, arguments can be omitted from right to left so long as they have defaults.